In performing editing operations on data stored within a memory unit, i.e., a database, and to increase the speed at which such changes may be made, a database checkout procedure may be utilized. In a database checkout procedure, a portion of the data, e.g., a file, from the database is locked for exclusive use and copied into a random access memory, i.e., a RAM. Subsequent read and write operations are then executed against the RAM copy. Once the edit operation is finished, the edited version of the data is checked back into the database and made available for general use. The older version of the data is removed, e.g., erased, from the memory unit or may be saved. This checkout/checkin procedure is referred to herein as database shadowing.
In database shadowing systems, it is preferred that access to data be fast and that changes and/or additions to the data within the database be reflected in a timely manner. Also, consistency, or at least identifiability, between edited versions of data is important. Otherwise, a user may not know which version of data is most current and usable.
It is therefore an object of the present invention to provide a database shadowing system which increases the access speed to data and reduces time required to make changes and/or additions to such data.
Another object of the present invention is to provide a database shadowing system which facilitates consistency between versions of edited data stored in a memory unit.